Four‐Quadrant Phase Mask Coronagraph with a Jacquinot‐Lyot Stop

Abstract

We report numerical simulations and laboratory demonstrations of a four-quadrant phase mask (FQPM) coronagraph equipped with a Jacquinot pupil as a Lyot stop. We demonstrate that the Jacquinot-Lyot stop can effectively suppress the residual stellar intensity due to tip-tilt errors for unresolved stars. We also show that the achievable contrast with the Jacquinot-Lyot stop depends on the direction of the tip-tilt errors, which suggests that the contrast can be improved if the direction of these errors is monitored simultaneously with the data acquisition. Furthermore, we conduct laboratory experiments with a polarization differential imager in which the Jacquinot-Lyot stop is introduced into a four-quadrant polarization mask (FQPoM) coronagraph. In these experiments we also demonstrate two image processing techniques, a cross-correlation technique and a polarization-degree analysis, to extract planetary signal from residual stellar speckle noise.